I think the ram is bad because i tried every thing increase cpu-nb voltage and ram voltage but nothing happened
well, your ram definitely MAY be the cause.
But, I wasn't sure on what kind of kingston ram you had. I have Kingston HyperX Blu 8gb 1600 DDR3 (2 sticks), and they do a great job when overclocked slightly. However, I haven't tested it with higher clocks around 1866mhz.
It definitely MAY be your cpu too. I was lucky enough to pick up a nice stable unlockable AMD Phenom II X4 960T and turned it into a X6 1600T overclocked @ 3.8 ghz with about 1.350v with .05v offset.
I can hit 4.0-4.5ghz as a X6 CPU with it but, I haven't taken it that far yet.
Your CPU VCORE voltage should not exceed 1.55v. However, it may be different for your CPU.
if you want to overclock your CPU for best performance and results, you need to consistently test your hardware and see what settings fit best as overclocking results will vary on each PC.
Also, if you're new to overclocking, DO NOT try anything until you get a aftermarket cooler such as the cheap yet, powerful CoolerMaster Hyper 212+.
Run Memtest or something to check if your ram is bad.
CPU: AMD Phenom II X4 960T: Unlocked: AMD Phenom II X6 1600T @ 3.8GHZ *24/7 OC*
MOBO: Gigabyte 970A-UD3
RAM: Kingston HyperX Blu 8gb DDR3 1600
HDD: Samsung Spinpoint F1 (F something) 1 TB
PSU: Stealthxstream 600w 80w certified.
GPU: XFX Radeon HD 6870 1GB